1. Field of the Invention
The present invention relates generally to communications between a host computer and an input/output adapter through an input/output fabric. More specifically, the present invention addresses where the input/output fabric is attached to more than one root node and where each root may potentially share with the other roots the input/output adapter.
2. Description of the Related Art
Standard peripheral component interconnect (PCI), and similar I/O fabric technologies, share one address space among the various root nodes, in a configuration with a plurality of root nodes, because no mechanism has been identified to separate the address spaces into independent address and configuration spaces. Thus, each root node has to be aware of the other root nodes' spaces, and not impinge on them. This is a problem with standard PCI configuration software, as they do not generally have this knowledge, and so such implementations will not work with current software, and in particular, existing configuration software. Furthermore, the concepts of logically partitioned systems are that the address spaces of partitions should be configurable so that they do not overlap, so that partitions may be kept independent, and no mechanism exist to do that today in the multi-root environment.
Thus it would be advantageous to provide a fully independent address and configuration space for each root node and for each partition or system image within a root node, so that existing software works and so that systems may be partitioned.